Question

Which part of cholesterol molecule is not embedded in the lipid bilayer?

(a) Hydroxyl end of cholesterol

(b) Entire molecule of cholesterol

(c) Hydrophobic rings

(d) Hydroxyl end and ^1⁄4th of the hydrophobic rings

I have been asked this question by my college professor while I was bunking the class.

My query is from Chemical Composition of Membranes topic in section Cellular Membranes of Cell Biology

Answer 1

Correct answer is (a) Hydroxyl end of cholesterol

The best explanation: Cholesterol molecules are oriented with their small hydrophilic hydroxyl groups toward the membrane surface and the remainder of molecule embedded in lipid bilayer. The hydrophilic rings of a cholesterol molecule are flat and rigid and interfere with the fatty acid tails of phospholipids.